wordy wednesday: behavior, cortisol, and welfare in horses

I’ve always wanted to put my research background to good use on this (or any) blog; writing in-depth but accessible articles knitting together research and results from multiple sources to bring a thorough and complete view to some complicated topics in equine science.  There is a crazy (though small) world of equine science out there: studies that explore everything from the effect of specific drugs on equine osteoarthritis to the interrelation of saddle slip and back shape on lameness in the ridden horse*.

Weirdly, I don’t seem to find time for that on the reg.

too busy doing this

Every once in a while I do come across a neat article about something equine-science related that I want to bring to you guys.  Frosting on the cherry is that this particular article is open access, so you can all read it if you want to!  And, in my opinion, it’s actually a fairly well-written and understandable study — perhaps because it tackles a fairly accessible topic that doesn’t require large amounts of jargon or a lifetime of studying some very specific mumbo-jumbo at 100x magnification to understand.

Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus)

Jodi Pawluski , Patrick Jego, Séverine Henry, Anaelle Bruchet, Rupert Palme, Caroline Coste, Martine Hausberger

Read the full text for yourself here.

I was originally attracted to this study because the write-up of it claimed there was some evidence in there that high cortisol levels in horses might correlate with a positive type of stress (excitement), as opposed to negative stress (poor welfare, having the snot beaten out of them, etc.).  It doesn’t quite show that, but it does cement some interesting and important findings.

1. Horse behavior can give us good insights to their welfare (duh, but read on a bit): horses that had an ears-back posture more than 50% of the time had lowered cortisol^ levels associated with hypothalamic-pituitary-adrenal (HPA) axis down-regulation (fancy way of saying their hormone pathways were messed up), which matched other studies. This means that both the behavior/posturing and testing of cortisol levels can be useful to equine welfare scientists in the future (within reason, of course).
2. Riding horses don’t think their lives are total shit, even when being ridden by amateurs.

In my opinion, one of the major strengths of this study is that the researchers used riding school horses in an active program (in France). Often, study subjects are kept in near hermetically-sealed conditions, in an attempt to control all external variables.  So an “inexperienced” person riding a horse in some studies is really someone who isn’t a legitimate professional, though can still course 3’6″.  While this is great for control — you know the rider isn’t likely to hurt the horse and can do exactly what you want them to do — it just doesn’t exhibit a lot of external validity — most horses don’t live their lives being ridden only by people capable of coursing 3’6″.  For the most part, being flopped around on by rank amateurs is a lot more like a horse’s experience.

floppy reality

So, what did the researchers actually find?  (In reverse order, because I’m trying to be confusing). #2 — horses did not experience a significant rise or fall in plasma cortisol or fecal glucocorticoid metabolites (FGMs).  This means that being ridden in a school program by kids who bop and pull and bounce and kick is not a significant positive or negative stressor for these horses.  Not enough to cause an acute or long-term rise or drop in FGMs or plasma cortisol. (Many caveats exist of course: these horses have been established in the lesson program for a while, meaning they didn’t flunk out so they must not hate it anyway; also, these horses had pretty astonishingly high levels of chiropractic issues — so many collinear factors here. You be the judge.)

And finding #1 — When we see horses with withdrawn behavior (in this study: ears back during feeding time, but in other studies: non-responsive behavior, facing a wall, reclusive in stall) we can pretty reasonably question whether or not their welfare might be compromised.  Just because a horse is a bit cranky doesn’t mean they have poor welfare, but it might be worth looking into.  The authors also looked into physiological measures (anemia and chiropractic issues), and there is definitely a feedback loop between psychological health, physical health, and welfare.  So we might consider that a horse who demonstrates a change in behavior, from generally perky to generally withdrawn or low-affect, might be experiencing something physical as well.

Interesting to note is that the researchers didn’t report anything about stereotypic behaviors like cribbing, weaving, etc.  I have done a lot of reading (in both horses and other species) about how stereotypic behavior might indicate welfare, and the literature is vast and, ultimately, equivocal: sometimes it means bad, sometimes it means nothing.

So there we have it. I really encourage you to read the full article if you have time, and tell me what you took from it!  We can start a little blogger journal club!

poor welfare or drugged?

* I have full access to these so please drop me a line if you’d like to know more.

^ Cortisol is often referred to as a “stress hormone”, but it really does and indicates so much more than that.  Cortisol is upregulated any time glycogen is turned into glucose to provide easily accessible energy to the muscles.  So obviously, this could be associated with both awesome exercise (like sex! or just running, I guess) and un-awesome exercise (running the fuck away from a lion). I will actually just direct you to the paper for more on this, since I feel that the authors did a really excellent job of explaining some of the complexity surrounding cortisol in the introduction.

Official stuff:

Article Source: Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus) 
Pawluski J, Jego P, Henry S, Bruchet A, Palme R, et al. (2017) Low plasma cortisol and fecal cortisol metabolite measures as indicators of compromised welfare in domestic horses (Equus caballus). PLOS ONE 12(9): e0182257. https://doi.org/10.1371/journal.pone.0182257

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